1) Field of the Invention
The present invention relates to a lens barrel with variable eyepoint position and a microscope using the same lens barrel. Hereafter, this type of lens barrel will be simply referred to as xe2x80x9cvariable lens barrelxe2x80x9d.
2) Description of Related Art
Various proposals have been made for a lens barrel used in microscopy regarding adjustment of the position at which the ocular is looked into (i. e. eyepoint) so as to allow an observer to easily perform observation in relaxed posture.
For example, Japanese Patent Application Preliminary Publication (KOKAI) No. Hei 4-166907 proposes a tilting lens barrel which is provided with a mechanism for adjusting the depression angle, or the angle in which an observer looks into the ocular of the binocular section. This configuration is intended to adjust the height and position of the eyepoint by changing the depression angle.
Also, Japanese Patent Application Preliminary Publication (KOKAI) No. Hei 8-278448 proposes to lower the eyepoint position by deflecting a beam of rays emergent from the objective using a deflecting member. The object of this proposal is to allow an observer to perform observation in relaxed posture by preliminarily lowering the eyepoint position.
Also, Japanese Patent Application Preliminary Publication (KOKAI) No. Hei 10-142473 proposes a lens barrel that is provided with a tilting mechanism for changing the depression angle and a mechanism for moving it along the observation optical axis. The object of this proposal is to change each of the height of the eyepoint position and the horizontal distance from the optical axis of the objective to the position of the eye of an observer.
Also, Japanese Patent Application Preliminary Publication (KOKAI) No. Hei 9-73031 discloses a microscope comprising an optical system that is made afocal between an objective and an imaging lens, which is housed in a movable lens barrel. The afocal beam between the objective and the imaging lens is deflected in the horizontal direction by a first deflecting member and is further deflected by 90xc2x0 by a second reflecting member, to enter the imaging lens. A guide is provided between the first deflecting member and the second reflecting member so that the second deflecting member and the movable lens barrel are integrally moved for changing the eyepoint position.
In microscopy, especially in the case where inspection of a large number of specimens or samples takes a long time, it is very important, for preventing fatigue of an observer/inspector and inaccurate inspection result caused by carelessness, to allow the observer to work in a relaxed posture. FIG. 22 shows the outer dimensions of an ordinary microscope. In order to relieve fatigue of each observer in the case where tall and large-built individuals and short and small-built individuals have to use a common microscope, it is important that values of 1) the height H from a desk top surface 2 to an eyepoint position E of an ocular OC, 2) the angle (depression angle) xcex8 at which the observer looks into the ocular OC, and 3) the horizontal distance d from the optical axis of an objective OB to the eyepoint position E of the ocular are appropriately set for each observer. In order to allow an observer of whatever build to perform long-time observation in a natural posture, the eyepoint position E of the ocular OC is required to be at the eyes of the observer under the condition where the observer puts the hand on a focusing wheel 3 in a natural posture. Regarding an ordinary microscope, the height of the specimen surface 1 from the desk top surface 2 is 200 mm, and the height of a lens barrel 4-side mount position 8 of a microscope body 5 is 305 mm from the desk top surface 2. In FIG. 22, the reference numeral 6 and the reference numeral 7 represent a condenser lens and a stage control, respectively.
If a titling lens barrel proposed by Japanese Utility Model Application Preliminary Publication (UM-KOKAI) No. 4-124218 is combined with this microscope, the minimum height of the eyepoint position E from the desk top surface 2 is approximately 400 mm. Also, since the tilting lens barrel can change the depression angle xcex8, the height from the desk top surface 2 is variable approximately in a range from 400 mm to 500 mm. Also, the distance from the optical axis of the objective OB to the center position of the focusing wheel 3 is approximately 100 mm. In the case of an ordinary lens barrel, the eyepoint position E is distant from the optical axis of the objective OB approximately by 195 mm. In the case of a tilting lens barrel, which can change the depression angle xcex8, the horizontal distance is variable approximately in a range from 140 mm to 195 mm.
If the depression angle xcex8 is changed using the above-mentioned tilting lens barrel, which simply changes the depression angle, the horizontal distance from the optical axis of the objective OB to the eyepoint position E is changed only by a small amount. However, the horizontal distance becomes shorter as the angle in reference to a horizontal plane is larger. This correlation makes it impossible to allow any observer of whatever build to perform observation in a natural posture. A tall and large-built person requires a longer horizontal distance from the optical axis of the objective and, as a matter of course, a higher eyepoint position than a short and small-built person does. For example, the optimum height of the eyepoint from the desk top surface 2 for a person of 1580 mm height is approximately 430 mm, whereas, for a person of 1840 mm height, the lowest necessary height of the eyepoint is approximately 510 mm from the desk top surface 2 and the optimum height of the eyepoint is approximately 600 mm from the desk top surface 2 on condition that the height of the desk top surface 2 from the floor is 70 cm and the height of a chair used during observation is appropriately adjusted. Therefore, even if the eyepoint height is adjusted to the maximum height using the conventional lens barrel 4, the person of 1840 mm height is obliged to keep an unnatural posture. In addition, the horizontal distance from the optical axis of the objective to the eyepoint also is too short, and, as a result, the posture of the observer looks as if he hunches over and hugs the microscope, to increase fatigue during observation, which is a problem. Also, even if an intermediate lens barrel is combined with the tilting lens barrel for adjustment of the eyepoint height, the eyepoint is allowed to be raised approximately by 60 mm at most, in effect. If the eyepoint is set higher than this limit, eclipse or short amount of marginal rays affects the image. As discussed above, use of the tilting lens barrel obliges a tall and large-built person to take an unnatural posture.
According to the lens barrel proposed by KOKAI No. Hei 10-142473, the depression angle and the eyepoint position are made variable independent of each other. However, in the lens arrangement of KOKAI No. Hei 10-142473, since a beam of rays from the objective is designed to be relayed to the focal plane of the ocular without imaging, a sufficiently long path length cannot be secured in the lens barrel. Therefore, it is substantially impossible to secure a sufficiently long horizontal distance from the objective to the eyepoint while providing a wide variable range of the eyepoint height for the above-mentioned adaptation of the microscope to variously built observers.
Also, within the scope of this conventional proposal, if the movable distance in the afocal section is designed to be long so as to allow the eyepoint position to be largely spaced away, the effective diameter through lenses and a binocular prism section becomes larger with degraded aberration performance by off-axial rays and the exit pupil position is largely displaced, to cause eclipse at the ocular.
Alternatively, if a design is made so that the afocal magnification of the first optical system and the second optical system is large and that the focal length of the third optical system is long for the purpose of spacing the eyepoint position away, the angle of an off-axial ray emergent from the second optical system becomes large, and, accordingly, the effective beam diameter becomes large in and after the third optical system, aberration performance on the margin is degraded, and inconsistency of the exit pupil position occurs.
Furthermore, in the case where a unit for reflecting illumination, a path dividing unit, a unit for raising the eyepoint position or the like is additionally arranged in the system, a beam diameter from the objective lens becomes large and accordingly effective beam diameter in the first optical system, the second optical system and the tilting mirror becomes large, to cause short amount of marginal rays or eclipse. Therefore, it is difficult to secure a long lens barrel length. If these optical systems are constructed to be large for adaptation to the large effective beam diameter, lenses cannot be arranged in a limited space.
To conclude, regarding the lens barrel proposed by KOKAI No. Hei 10-142473, it is difficult to secure a sufficient horizontal distance from the optical axis of the objective to the eyepoint position. Also, the movable distance of the third optical system using the afocal section is 30 mm at most. Therefore, it is difficult to allow variously built observers, especially tall and large-built persons, to take an optimum posture for observation. In addition, this prior example fails to disclose particular numerical data such as the height of the eyepoint position and the horizontal distance from the optical axis of the objective to the eyepoint position and thus its superiority to the conventional lens barrel at that time is not clear.
Similarly, according to the proposal of KOKAI No. 9-73031 also, since movable range of the lens unit for changing the length of the afocal beam of rays is physically limited, the eyepoint position cannot be changed so large as to be well adapted to variously built observers.
The present invention is made in consideration of the aforementioned problems of the conventional art. An object of the present invention is to provide a variable lens barrel which can change the horizontal distance from the optical axis of the objective to the eyepoint position, the height of the eyepoint, and the depression angle for observation so that a person of any build is able to perform observation in a natural posture causing little fatigue and which can achieve system compatibility with intermediate lens barrels etc. The present invention is directed to a microscope using such a variable lens barrel, also.
In order to attain the above-mentioned objects, a lens barrel according to the present invention comprises, in order from the light incident side, a first optical system, a second optical system which converts a beam of rays emergent from the first optical system into a parallel beam of rays, and a third optical system which introduces the beam of parallel rays emergent from the second optical system into an ocular. The first optical system includes a lens unit which forms an intermediate image and at least three light deflecting members which deflect the beam of rays. The second optical system includes a lens unit and a light deflecting member. The light deflecting member of the second optical system is constructed and arranged to turn around an axis that is perpendicular to a first optical axis and a second optical axis, where the center axis of the beam of rays emergent from the most second optical system-side one of the light deflecting members of the first optical system in optical arrangement is defined as the first optical axis, and the center axis of the beam of parallel rays emergent from the second optical system is defined as the second optical axis.
According to this configuration, an intermediate image is formed by the first optical system, is re-imaged by the second optical system and the third optical system at the focal plane of the ocular, and is observed. For image observation via the ocular without eclipse, the entrance pupil position of the ocular is required to substantially coincide with the exit pupil position of the lens barrel. For this arrangement, it is necessary to form an afocal system with the second optical system and the third optical system. Under this condition, if each lens unit of the second optical system and the third optical system is constructed with a cemented lens, separation as much as F2+F3 is required between the second optical system and the third optical system, where the focal length of the second optical system is F2 and the focal length of the third optical system is F3. Also, since the intermediate image by the first optical system is converted into a beam of parallel rays, if the lens unit of the first optical system is constructed of a single lens, the separation between the first optical system and the second optical system becomes F1+F2, where the focal length of the first optical system is F1.
In this way, the configuration in which an intermediate image is formed inside the lens barrel can secure a sufficiently long path length of the optical systems arranged in the lens barrel in comparison with a configuration without an intermediate image. Accordingly, a wide variety of options are available regarding the path layout inside the lens barrel, and thus higher flexibility is assured in eyepoint position setting.
Also, since at least three optical members and, in addition, an optical member that it to turn freely are arranged in the lens barrel for deflecting the beam of rays, the beam of rays are deflected four times inside the lens barrel, to allow observation of a correctly erected image. Also, revolving movement of the light deflecting member of the second optical system, the rear section of the second optical system arranged behind the light deflecting member of the second optical system, the third optical system and the ocular allows adjustment of the depression angle for observation.
Also, according to the present invention, the lens barrel is constructed and arranged so that, when the light deflecting member of the second optical system is turned by an angle of xcex1, a rear section of the second optical system disposed behind the light deflecting member of the second optical system, the third optical system and the ocular are integrally revolved by an angle of 2xcex1.
According to this configuration, since the axis of the beam of rays emergent from the light deflecting member of the second optical system and the optical axis of the ocular always coincide, correction of the depression angle in accordance with turn of the light deflecting member is dispensable, to provide a highly operable microscope.
Also, according to the present invention, the lens barrel is constructed and arranged so that the separation between the second optical system and the third optical system is variable along the optical axis.
According to this configuration, it is possible to change the eyepoint position by integrally moving the third optical system and the ocular in the direction of the optical axis of the third optical system. Also, as described above, the depression angle, at which an observer looks into the ocular, can be changed by revolving movement of the light deflecting member of the second optical system. Therefore, combination of these features allows the eyepoint position to be changed in height and in distance from the optical axis of the objective.
Also, a lens barrel according to the present invention comprises, in order from the light incident side, a first optical system, a second optical system which converts a beam of rays emergent from the first optical system into a beam of parallel rays, and a third optical system which introduces the beam of parallel rays emergent from the second optical system into an ocular. The first optical system comprises a lens unit which forms an intermediate image and at least four light deflecting members which deflect the beam of rays. The separation between the second optical system and the third optical system is variable in a direction along the center axis of the beam of rays emergent from the second optical system.
According to this configuration, as in the aforementioned configuration, the intermediate image is formed by the first optical system, is re-imaged by the second optical system and the third optical system at the focal plane of the ocular, and is observed. In this way, the configuration in which the intermediate image is formed inside the lens barrel can secure a sufficiently long path length of the optical systems arranged in the lens barrel in comparison with a configuration without an intermediate image. Accordingly, a wide variety of options are available regarding the path layout inside the lens barrel, and thus higher flexibility is assured in eyepoint position setting.
Also, in the lens barrel, at least four optical members and, in addition, an optical member that it to turn freely are constructed and arranged to deflect the beam of rays six times inside the lens barrel, so that a correctly erect image can be observed.
Furthermore, since the lens barrel is designed so that the beam of rays traveling between the second optical system and the third optical system is parallel, the imaging performance and the image position do not change even if the separation between the second optical system and the third optical system is changed. Accordingly, the third optical system and the ocular are allowed to integrally move in the direction of the optical axis of the third optical system and thus the eyepoint position can be changed.
Also, according to the present invention, the third optical system comprises, in order from the side of the second optical system, a first lens unit having a positive refracting power, a second lens unit having a negative refracting power, and a third lens unit having a positive refracting power.
According to this configuration, since the separation between the second optical system and the third optical system is allowed to be shorter than in a configuration where the third optical system is composed of a single lens (which may be a cemented lens) and accordingly the pupil position of the ocular can be set closer to the third optical system, a conventional ocular is commonly usable or eclipse at the ocular is avoidable.
As will be described later in the first embodiment, in a configuration where the third optical system is composed of a single cemented lens, if the separation between the second optical system and the third optical system is short, the pupil position at the focal plane of the ocular comes closer to the ocular. As a result, such a phenomenon as limits the optical performance of the ocular, e.g., increase in effective diameter of the ocular, eclipse on the margin, takes place. In addition, since a large separation is necessary between the second optical system and the third optical system, the path length of the entire system becomes long, to cause bulkiness of the lens barrel itself. In contrast, in the above-mentioned configuration where the third optical system is composed of three lens units of positive-negative-positive, a path length (space) to accommodate the prism section can be secured in the lens barrel. Furthermore, this configuration can reduce change of the entrance pupil position on the side of the objective, which would be caused by use in combination with an intermediate lens barrel, and fluctuation of the exit pupil, which would be caused in accordance with integral movement of the third optical system through the ocular. Also, eclipse or short amount of marginal rays can be prevented without increase in the effective diameter of each lens arranged in the third optical system through the ocular. In addition, since the total path length can be shortened, compact sizing of the entire lens barrel can be realized.
Also, in the third optical system of the present invention, the first lens unit comprises at least one positive meniscus lens which directs a concave surface thereof toward the second lens unit, and the third lens unit comprises at least one positive meniscus lens which directs a concave surface thereof toward the second lens unit.
This configuration can well reduce generation of aberrations caused by off-axial rays and can maintain the performance in good condition regarding off-axial aberrations, which would be affected by fluctuation of the exit pupil position in accordance with the integral movement of the third optical system through the ocular.
Also, the lens barrel according to the present invention is constructed and arranged to satisfy the condition:
0.7xe2x89xa6F1/Fxe2x89xa61.4 
where F1 is the focal length of the first optical system, and F is the focal length of the entire system from the first optical system through the third optical system.
According to this configuration, The lens barrel can be made compact, without increase in lens diameter or unnecessary prolongation of the path length inside the lens barrel. Furthermore, the horizontal distance from the optical axis of the objective to the eyepoint position can be set long. Furthermore, regarding the eyepoint height, it can be set higher than in the case of the conventional lens barrel. Furthermore, combination with the above-mentioned configuration in which the third optical system through the ocular are integrally movable allows the horizontal distance from the optical axis of the objective to the eyepoint position to be largely changed and allows the depression angle also to be changed. As a result, the eyepoint position can be set more flexibly in a wider range and thus the observer of whatever build can take an ideal posture for observation.
If F1/F falls below the lower limit of the condition in the case where the value of the focal length F2 of the second optical system is larger than F1, the focal length F3 (=(F2/F1)xc3x97F) of the third optical system becomes longer than F and accordingly the length from the third lens unit to the ocular becomes long. Under this condition, since the eyepoint position is too distant from the optical axis of the objective, appropriate posture for observation cannot be taken. In the case where the value of F2 is smaller than F1, while the path length can be made short, aberrations cannot be compensated in good condition or a field lens for adjustment of the pupil position is necessitated, to result in increase in number of lenses and accordingly cost rise of the products.
Also, if an intermediate lens barrel is interposed between the infinity distance correcting objective and the lens barrel, to widen the separation between, eclipse or degradation of the off-axial aberration performance would be caused. Therefore, too small value of F1/F is not preferable in view of system compatibility also.
If F1/F exceeds the upper limit of the condition in the case where the value of F2 is smaller than F1, F3 also becomes small, and accordingly a sufficient path length cannot be secured in the binocular section as to accommodate the prisms. Also, the lens diameter of the third optical system and the prism size of the binocular section are obliged to be large. As a result, the parts used in the lens barrel cannot be standardized with the parts of the conventional binocular section, to raise cost of the products. Also, under the condition where the separation between the infinity distance correcting objective and the lens barrel is small, the pupil position is not properly located and thus eclipse or degradation of aberration performance on the margin occurs. Therefore, too large value of F1/F is not preferable.
Also, the lens barrel according to the present invention is configured to satisfy the following condition:
0.5xe2x89xa6F3/Fxe2x89xa61 
where F3 is the focal length of the third optical system.
This configuration allows aberrations to be compensated in good condition. Therefore, eclipse of the field or short amount of light on the margin resulting from shift of the pupil position less occurs even if the pupil position is changed in accordance with integral movement of the third optical system through the ocular or with interposition of an intermediate lens barrel unit between the objective and the lens barrel. Also, layout of the path of rays in the lens barrel can be made compact and the eyepoint can be set at a position more distant than in the case of the conventional lens barrel. Therefore, this configuration is preferable.
If F3/F falls below the lower limit of the condition, the path length in the lens barrel becomes extremely long to cause bulkiness of the lens barrel or, alternatively, F3 is made short and accordingly a sufficient path length cannot be secured between the third optical system and the ocular. Also, the pupil position cannot substantially coincide with the entrance pupil position of the ocular and accordingly eclipse or degradation of off-axial aberration performance is caused.
If F3/F exceeds the upper limit of the condition, since the F3 is long and accordingly the path length from the third optical system to the ocular becomes long, the eyepoint position is too distant from the optical axis of the objective, and, in addition, the total path length also becomes long, to result in bulkiness of the lens barrel. Therefore, too large value of F3/F is not preferable. Also, since the pupil position cannot substantially coincide with the entrance pupil position of the ocular, unfavorable phenomenon such as eclipse or degradation of off-axial aberration performance occurs as in the case where F3/F is below the lower limit.
This and other objects as well as features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings.